1. Field of the Invention
The present invention relates to an ultrasonic treatment appliance for incising or coagulating a living tissue by utilizing ultrasonic waves with the living tissue clamped by a clamping member.
2. Description of the Related Art
U.S. Pat. No. 5,322,055 has presented an appliance for treating a living tissue ultrasonically. Herein, the living tissue is clamped between the distal part of a probe, which serves as a vibration transmission member, and a clamping member that is opposed to the distal part of the probe and can rotate freely.
This type of ultrasonic treatment appliance clamps a living tissue to be coagulated or resected by the distal part of a probe and a clamping member. The clamped living tissue may be a very soft tissue such as a vessel or the fat or only a small portion of the living tissue may be clamped. In this case, a very large quantity of clamping force is not needed to coagulate or resect the living tissue.
However, for coagulating or resecting a large portion of a tissular region that is relatively hard to resect, such as, a parenchymal organ, for example, the liver or duodenum, a large quantity of clamping force is needed.
In this case, a large bending stress is applied to the probe. This causes the probe to warp in a direction in which the clamping member closes, that is, in a direction in which the probe recedes from the clamping member. In general, the clamping member is designed to press all positions of the probe with the same load. When the clamping member is clamping a living tissue, a uniform load is applied to the probe.
At this time, the magnitude of the bending stress applied to the probe depends greatly on the sectional shape of the clamping member of the probe, that is, a section modulus thereof.
At present, as described in the specification of the U.S. Pat. No. 5,322,055, the sectional shape of a clamping member of a probe is constant relative to the longitudinal direction of the probe.
Now, actual treatment will be discussed.
The smaller the diameter of the probe is, the larger field of view is provided near the probe tip. This permits adroit manipulation for treatment. However, the probe is shaped so that only a small section modulus is exhibited for a normal stress applied to the probe. The probe therefore warps.
Moreover, the outer diameter of an insertion unit of a hand-held piece of the foregoing current ultrasonic treatment appliance is approximately 10 mm. When an attempt is made to design the hand-held piece so that the outer diameter will be, for example, 5 mm or 3 mm, the sectional area of the probe must be made smaller than the current one. At this time, the probe exhibits a much smaller section modulus for a normal stress necessary to coagulate or resect a tissue.
When a probe is shaped to exhibit a constant section modulus, which is smaller than a certain value, over the whole area of the distal part of the probe, a quantity of clamping force, that is, a normal stress becomes large. This causes the probe to warp.
Once a probe warps, when the probe clamps a tissue in cooperation with a clamping member, the probe will not mesh with the clamping member properly. In other words, the roots of the probe and clamping member have such a positional relationship that the tissue cannot be coagulated or resected, because the tissue is sticking to the probe and clamping member. Nevertheless, the tips of the probe and clamping member have such a positional relationship that the tissue cannot be coagulated or resected, because the tips are spaced. This poses a problem of a deteriorated ability to resect a tissue.
Moreover, an operator may handle the probe to limit the movements of the clamping member in an effort to decrease a quantity of applied clamping force. This is intended to prevent the probe from warping and prevent the probe and clamping member from having the positional relationship disabling coagulation and resection. As a result, the quantity of clamping force becomes too small. Consequently, the problem of a deteriorated ability to resect a tissue arises.
Furthermore, there is another problem that especially the top of a probe is prone to a flaw.
For example, another treatment appliance may be held by mistake during an actual surgical procedure or during ultrasonic oscillation. In this case, it is unavoidable that the top of the probe is flawed, though the flow is small.
Moreover, when a burn of a tissue sticks on the top of the probe, it may be removed by performing cleaning after use. In this case, when a sharp cleaning tool is used to scrub the top of the probe, the probe may be flawed.
Moreover, some ultrasonic treatment appliances including the one disclosed in Japanese Unexamined Patent Publication No. 10-127654 have a metallic probe opposed to a clamping member. In this case, the probe and clamping member rubs against each other at every ultrasonic oscillation. The probe may flow.
Any of the ultrasonic treatment appliances has a structure prone to flaw, that is, undergo a small crack near the top of the probe.
Assume that although a small crack has occurred on the top of a probe, the probe is used to clamp a living tissue and vibrated ultrasonically. In this case, a stress is induced by ultrasonic vibration (in this case, the stress becomes maximum at a node of an ultrasonic wave and becomes minimum at an antinode thereof). Moreover, a bending moment is developed in the probe by clamping the tissue. The stress and bending moment are compounded to bring about a situation of stress distribution. In this situation, the actions of all moments work on the flaw on the top of the probe. Especially, the bending moment developed by clamping a tissue acts as a load stress causing the flaw on the top of the probe to develop. If oscillation is repeated in this state, there arises a fear that a fatigue crack occurs with the flaw as a starting point.
Moreover, Japanese Unexamined Patent Publication No. 8-275949 has disclosed an ultrasonic incision/coagulation appliance in which a clamping surface used to reliably clamp a living tissue has an irregular part. In this appliance, the irregular part of the clamping surface acts as a portion on which a stress is concentrated, and thus becomes a factor of a crack. It is therefore impossible to expect improvement in durability of a probe. Besides, when the clamping surface is rubbed against a tissue, since a contact area is limited, frictional heat hardly occurs. This disrupts anticipation of stable coagulation or resection.
Furthermore, ultrasonic incision/coagulation appliances disclosed in Japanese Unexamined Patent Publications Nos. 8-275950 and 9-38099 are analogous to the appliance in the Japanese Unexamined Patent Publication No. 8-275949. That is to say, a clamping surface used to reliably clamp a living tissue has an irregular part.
Incidentally, even when a solid probe free from a bending moment is vibrated ultrasonically, a fatigue failure will not occur. Moreover, it is experimentally confirmed that even if a small crack occurs, the crack will not develop.
An object of the present invention is to provide an ultrasonic treatment appliance in which a warp of a probe occurring when a living tissue is clamped is restrained.
Another object of the present invention is to provide an ultrasonic treatment appliance having stable coagulating and resecting abilities.
Still another object of the present invention is to provide an ultrasonic treatment appliance in which the durability of a probe has been improved.
Briefly, an ultrasonic treatment appliance in accordance with the present invention offers stable treatability and enjoys excellent durability. The ultrasonic treatment appliance consists of: an ultrasonic transducer unit having an ultrasonic transducer, which produces ultrasonic waves, incorporated in a hand-held piece; a probe connected to a horn that amplifies ultrasonic waves produced by the ultrasonic transducer, and serving as a vibration transmission member; a treatment member located at the distal end of the probe, having an ultrasonic treatment surface that is parallel to the longitudinal axial direction of the probe and is flat, exhibiting a larger section modulus in the proximal part thereof than in the distal part thereof, and having ultrasonic waves transmitted thereto; a clamping member, opposed to the treatment member, for clamping a living tissue in cooperation with the treatment member; and a clamping manipulation unit for use in moving at least one of the treatment member and clamping member so as to clamp a living tissue between the treatment member and clamping member.